1. Field of the Invention
This invention relates generally to the production of nanostructures. It relates particularly to the formation of at least centimeter-long stranded boron nitride nanotube fibers.
2. Description of the Related Art
Since the announcement of the successful synthesis of high-aspect-ratio few-walled boron nitride nanotubes (FW-BNNTs) in 1995, little progress has been made in the scale-up of their synthesis. As a demonstration, in spite of the theoretical capabilities of FW-BNNTs to provide high strength-to-weight, high temperature resistance, piezo-electric actuation, and radiation shielding (via the boron content), the aerospace industry still relies on micron-sized graphite or boron fibers for structural applications. Neither FW-BNNTs nor single-wall carbon nanotubes are widely used in aerospace manufacturing, the industry generally most willing to pay a premium for high performance.
To date, high-aspect ratio FW-BNNTs have been produced in small amounts (from individual tubes to milligrams) by arc-discharge or laser heating methods. A separate class of boron nitride nanotubes has also been produced by chemical vapor deposition of nitrogen compounds (e.g. ammonia) over ball-milled precursors, but these tubes are of larger diameter and do not exhibit the continuous crystalline sp2-type bonding structure which has drawn most theoretical interest.